diff --git a/interop/grpclb_fallback/client.go b/interop/grpclb_fallback/client.go
index 77aac1a6..a552a66d 100644
--- a/interop/grpclb_fallback/client.go
+++ b/interop/grpclb_fallback/client.go
@@ -1,3 +1,4 @@
+// +build linux
 // +build !appengine
 // +build go1.11